Abstract
Musculoskeletal disorders (MSDs) are comprised of a wide range of pathological states including inflammatory and degenerative conditions affecting the muscles tendons, ligaments, joints, central and peripheral nerves, and supporting blood vessels of the human body. In addition, they constitute a significant proportion of all reported and/or compensable work-related diseases contributing to substantial numbers of lost work days and medical care utilization in the United States. MSDs have multiple and inter-connected risk factors, both occupational and non-occupational such as repetitive trauma, obesity, smoking, drinking, and physical activity. At the present time, the associations between US worker occupation/industry, health behaviors, health-related quality of life, geographic variations, and MSDs have not been thoroughly investigated. While the relationship between MSDs and work-related injuries has been comprehensively characterized with particular occupational exposures, this relationship in large nationally representative worker populations has not been examined. Using the 1997-2008 National Health Interview Survey (NHIS) Study Database and the 2001-2003 Medical Expenditure Panel Survey (MEPS), this dissertation examined musculoskeletal disorders in the US workforce, focusing on the under-explored associations between US worker occupation, health behaviors (physical activity patterns, obesity, and cigarette smoking), geographical location, and health-related quality of life impact of musculoskeletal disorders. The overall prevalence of arthritis was 21.7% with 14.2% for employed adults and variation in rates by occupation type (e.g., Computer/Mathematical occupations [11.2%] versus Healthcare support occupations [17.5%]). Overall rates of specific arthritis conditions, which also varied by occupation included: arthritis (19.3%), rheumatoid arthritis (2.3%), gout (1.4%), lupus (0.3%), and fibromyalgia (1.2%). Using a structural equation model with latent variables approach, we found that a two latent factor (gross and fine-motor functional limitations) model had good model fit among US workers with arthritis. Health behaviors mediated the relationship between occupation and both motor functional limitations. Workers with arthritis that were current smokers and did not engage in physical activity reported significantly greater levels of both types of motor functional limitations. Lastly, at age 25, blue-collar workers can expect to live 44 years of perfect health over their remaining life, while white-collar workers can expect to live 50. Among those with arthritis, QALE is 33 and 39 respectively. Said another way, blue-collar workers with arthritis can look forward to 17 fewer years of perfect health. At age 65, white-collar workers with arthritis who remain in the workforce can expect to lose just 4 QALYs relative to those without arthritis, while blue-collar workers lose nearly 6 of their remaining years of perfect health measured in QALYs. Musculoskeletal disorders are prevalent in the US workforce, vary by occupation/industry type, and can become disabling conditions that both consume a large proportion of health care resources and are the leading cause of functional loss in adults. Health behaviors appear to partially mediate the relationship between musculoskeletal conditions and functional limitations. Work disability related to MSDs is a challenge to employability, business productivity, and the capacity of health and social security systems. Preventive efforts to decrease sick leave due to MSDs may include measures to increase the occurrence of positive health behaviors at work and to minimize repetitive work procedures. Targeted research efforts among workers with arthritis that reduce the presence of harmful workplace exposures, enhance workplace accommodations and educate on the deleterious effects of negative health behaviors are warranted. Future occupational surveillance systems should develop robust self-reported and biological measurements to document and examine MSDs in the US workforce.